PLATE 25. 



Fig. 24. Cylindrospermum licheniforme. Longitudinal section of two cells 

 and a heterocyst. Living material. Ziel's carbol fuchsin, counter- 

 stained with wasserblau. The fuchsin kills and stains the cytoplasm 

 and the chromatin. The wasserblau restains these same parts and 

 brings out the £ granules. 



Fig. 25. Same species, view and treatment as Fig. 24, except the counter- 

 staining with wasserblau. 



Fig. 26. Same species and view as Figs. 24 and 25. K. I. Aqueous methy- 

 lene blue. 



Fig. 27. Oscillatoria brevis var. Longitudinal section. K. I. Overstained 

 with fuchsin and only partially washed out, showing the nucleus with 

 well defined outline, but the internal structure not differentiated. 



Fig. 28. Beggiatoa arachnoidea. Longitudinal section. K. I. washed in 

 95 per cent, alcohol 2 hours to remove iodine and the sulphur gran- 

 ules. Aqueous methylene blue, showing a continuous coarse network 

 which extends to the surface at only a few points. The cytoplasm is 

 made up of a very fine network around the periphery. The cell mem- 

 brane is very delicate. The red granules are probably the same as 

 the a granules in the Cyanophyceae. 



Fig. 29. Cross section of same species as Fig. 28 treated in the same 

 manner. 



Fig. 30. Oscillatoria limosa. Cross section. K. I. Aqueous thinonin, coun- 

 terstained with wasserblau and washed in acidulated alcohol. Both 

 a and ]Q granules are shown, and lightly stained chromatin. 



[294] 



